A conventional field emission display mainly comprises a cathode plate module and an anode plate module. As shown in FIG. 1, the front light FED mainly comprises a cathode plate and an anode plate. The cathode plate comprises a first substrate 101, plural cathode lines 103, plural gate lines 105, a plurality of emitters 107, and a dielectric layer 109. All of the cathode lines 103, the gate lines 105, the emitters 107 and the dielectric layer 109 are formed on the surface of the first substrate 101. The anode plate comprises a second substrate 111, an Indium Tin Oxide (ITO) layer 113 formed on the inner surface of the second substrate 111, and a phosphor layer 115 formed on the top of the ITO layer 113. Electrons emitted from emitters 107 hit the phosphor layer 115 and trigger the phosphor layer 107. The light source triggered by the phosphor layer 107 passes through the anode plate, and is released from the outer surface of the anode plate.
Researches on enhancing the luminance and uniformity of the flat panel light sources for FEDs are still on the way of evolving. One of the researches is for an FED backlight source. The FED backlight source is featured with an extra reflection structure on the anode plate. The added reflection structure reflects the light source triggered by the phosphor onto the cathode plate, and the light source is released from the outer surface of the cathode plate.
Spacers have been used to provide the supporting between the cathode plate and the anode plate in the packaging process for an FED light source. The technology of using spacers has long been criticized for the need for a high width-to-height ratio to minimize the display area blocked by the spacers. By a low drive voltage of electrons, the light source triggered by the phosphor layer may not have satisfactory luminance. To enhance the luminance with the conventional high drive voltage phosphor layer, the voltage between anode electrodes and cathode electrodes has to be increased to grant electrons enough energy on the phosphor layer. The increased voltage disadvantages itself with the current leakage problem. To prevent current leakage, the anode-cathode gap has to be increased. As a result of the increased anode-cathode gap, there is a need for an even higher width-to-height ratio for spacers in order not to affect the quality of the display area. This thus makes the spacer manufacturing even harder.